/*
 *********************************************************************************************************
 *                                                uC/OS-II
 *                                          The Real-Time Kernel
 *                                          SEMAPHORE MANAGEMENT
 *
 *                          (c) Copyright 1992-2006, Jean J. Labrosse, Weston, FL
 *                                           All Rights Reserved
 *
 * File    : OS_SEM.C
 * By      : Jean J. Labrosse
 * Version : V2.83
 *********************************************************************************************************
 */

#ifndef  OS_MASTER_FILE
#include <ucos_ii.h>
#endif

#if OS_SEM_EN > 0
/*
 *********************************************************************************************************
 *                                           ACCEPT SEMAPHORE
 *
 * Description: This function checks the semaphore to see if a resource is available or, if an event
 *              occurred.  Unlike OSSemPend(), OSSemAccept() does not suspend the calling task if the
 *              resource is not available or the event did not occur.
 *
 * Arguments  : pevent     is a pointer to the event control block
 *
 * Returns    : >  0       if the resource is available or the event did not occur the semaphore is
 *                         decremented to obtain the resource.
 *              == 0       if the resource is not available or the event did not occur or,
 *                         if 'pevent' is a NULL pointer or,
 *                         if you didn't pass a pointer to a semaphore
 *********************************************************************************************************
 */

#if OS_SEM_ACCEPT_EN > 0
INT16U  OSSemAccept(OS_EVENT *pevent)
{
    INT16U cnt;

#if OS_CRITICAL_METHOD == 3                           /* Allocate storage for CPU status register      */
    OS_CPU_SR cpu_sr = 0;
#endif



#if OS_ARG_CHK_EN > 0
    if (pevent == (OS_EVENT*)0)                       /* Validate 'pevent'                             */
    {
        return 0;
    }
#endif
    if (pevent->OSEventType != OS_EVENT_TYPE_SEM)     /* Validate event block type                     */
    {
        return 0;
    }
    OS_ENTER_CRITICAL();
    cnt = pevent->OSEventCnt;
    if (cnt > 0)                                      /* See if resource is available                  */
    {
        pevent->OSEventCnt--;                         /* Yes, decrement semaphore and notify caller    */
    }
    OS_EXIT_CRITICAL();
    return cnt;                                       /* Return semaphore count                        */
}
#endif

/*$PAGE*/
/*
 *********************************************************************************************************
 *                                           CREATE A SEMAPHORE
 *
 * Description: This function creates a semaphore.
 *
 * Arguments  : cnt           is the initial value for the semaphore.  If the value is 0, no resource is
 *                            available (or no event has occurred).  You initialize the semaphore to a
 *                            non-zero value to specify how many resources are available (e.g. if you have
 *                            10 resources, you would initialize the semaphore to 10).
 *
 * Returns    : != (void *)0  is a pointer to the event control clock (OS_EVENT) associated with the
 *                            created semaphore
 *              == (void *)0  if no event control blocks were available
 *********************************************************************************************************
 */

OS_EVENT  *OSSemCreate(INT16U cnt)
{
    OS_EVENT  *pevent;

#if OS_CRITICAL_METHOD == 3                                /* Allocate storage for CPU status register */
    OS_CPU_SR cpu_sr = 0;
#endif



    if (OSIntNesting > 0)                                  /* See if called from ISR ...               */
    {
        return (OS_EVENT*)0;                               /* ... can't CREATE from an ISR             */
    }
    OS_ENTER_CRITICAL();
    pevent = OSEventFreeList;                              /* Get next free event control block        */
    if (OSEventFreeList != (OS_EVENT*)0)                   /* See if pool of free ECB pool was empty   */
    {
        OSEventFreeList = (OS_EVENT*)OSEventFreeList->OSEventPtr;
    }
    OS_EXIT_CRITICAL();
    if (pevent != (OS_EVENT*)0)                            /* Get an event control block               */
    {
        pevent->OSEventType    = OS_EVENT_TYPE_SEM;
        pevent->OSEventCnt     = cnt;                      /* Set semaphore value                      */
        pevent->OSEventPtr     = (void*)0;                 /* Unlink from ECB free list                */
#if OS_EVENT_NAME_SIZE > 1
        pevent->OSEventName[0] = '?';                      /* Unknown name                             */
        pevent->OSEventName[1] = OS_ASCII_NUL;
#endif
        OS_EventWaitListInit(pevent);                      /* Initialize to 'nobody waiting' on sem.   */
    }
    return pevent;
}

/*$PAGE*/
/*
 *********************************************************************************************************
 *                                         DELETE A SEMAPHORE
 *
 * Description: This function deletes a semaphore and readies all tasks pending on the semaphore.
 *
 * Arguments  : pevent        is a pointer to the event control block associated with the desired
 *                            semaphore.
 *
 *              opt           determines delete options as follows:
 *                            opt == OS_DEL_NO_PEND   Delete semaphore ONLY if no task pending
 *                            opt == OS_DEL_ALWAYS    Deletes the semaphore even if tasks are waiting.
 *                                                    In this case, all the tasks pending will be readied.
 *
 *              err           is a pointer to an error code that can contain one of the following values:
 *                            OS_NO_ERR               The call was successful and the semaphore was deleted
 *                            OS_ERR_DEL_ISR          If you attempted to delete the semaphore from an ISR
 *                            OS_ERR_INVALID_OPT      An invalid option was specified
 *                            OS_ERR_TASK_WAITING     One or more tasks were waiting on the semaphore
 *                            OS_ERR_EVENT_TYPE       If you didn't pass a pointer to a semaphore
 *                            OS_ERR_PEVENT_NULL      If 'pevent' is a NULL pointer.
 *
 * Returns    : pevent        upon error
 *              (OS_EVENT *)0 if the semaphore was successfully deleted.
 *
 * Note(s)    : 1) This function must be used with care.  Tasks that would normally expect the presence of
 *                 the semaphore MUST check the return code of OSSemPend().
 *              2) OSSemAccept() callers will not know that the intended semaphore has been deleted unless
 *                 they check 'pevent' to see that it's a NULL pointer.
 *              3) This call can potentially disable interrupts for a long time.  The interrupt disable
 *                 time is directly proportional to the number of tasks waiting on the semaphore.
 *              4) Because ALL tasks pending on the semaphore will be readied, you MUST be careful in
 *                 applications where the semaphore is used for mutual exclusion because the resource(s)
 *                 will no longer be guarded by the semaphore.
 *********************************************************************************************************
 */

#if OS_SEM_DEL_EN > 0
OS_EVENT  *OSSemDel(OS_EVENT *pevent, INT8U opt, INT8U *err)
{
    BOOLEAN tasks_waiting;
    OS_EVENT  *pevent_return;

#if OS_CRITICAL_METHOD == 3                                /* Allocate storage for CPU status register */
    OS_CPU_SR cpu_sr = 0;
#endif



#if OS_ARG_CHK_EN > 0
    if (err == (INT8U*)0)                                  /* Validate 'err'                           */
    {
        return pevent;
    }
    if (pevent == (OS_EVENT*)0)                            /* Validate 'pevent'                        */
    {
        *err = OS_ERR_PEVENT_NULL;
        return pevent;
    }
#endif
    if (pevent->OSEventType != OS_EVENT_TYPE_SEM)          /* Validate event block type                */
    {
        *err = OS_ERR_EVENT_TYPE;
        return pevent;
    }
    if (OSIntNesting > 0)                                  /* See if called from ISR ...               */
    {
        *err = OS_ERR_DEL_ISR;                             /* ... can't DELETE from an ISR             */
        return pevent;
    }
    OS_ENTER_CRITICAL();
    if (pevent->OSEventGrp != 0)                           /* See if any tasks waiting on semaphore    */
    {
        tasks_waiting = OS_TRUE;                           /* Yes                                      */
    }
    else
    {
        tasks_waiting = OS_FALSE;                          /* No                                       */
    }
    switch (opt)
    {
    case OS_DEL_NO_PEND:                                   /* Delete semaphore only if no task waiting */
        if (tasks_waiting == OS_FALSE)
        {
#if OS_EVENT_NAME_SIZE > 1
            pevent->OSEventName[0] = '?';                  /* Unknown name                             */
            pevent->OSEventName[1] = OS_ASCII_NUL;
#endif
            pevent->OSEventType    = OS_EVENT_TYPE_UNUSED;
            pevent->OSEventPtr     = OSEventFreeList;      /* Return Event Control Block to free list  */
            pevent->OSEventCnt     = 0;
            OSEventFreeList        = pevent;               /* Get next free event control block        */
            OS_EXIT_CRITICAL();
            *err                   = OS_NO_ERR;
            pevent_return          = (OS_EVENT*)0;         /* Semaphore has been deleted               */
        }
        else
        {
            OS_EXIT_CRITICAL();
            *err                   = OS_ERR_TASK_WAITING;
            pevent_return          = pevent;
        }
        break;

    case OS_DEL_ALWAYS:                                    /* Always delete the semaphore              */
        while (pevent->OSEventGrp != 0)                    /* Ready ALL tasks waiting for semaphore    */
        {
            (void)OS_EventTaskRdy(pevent, (void*)0, OS_STAT_SEM);
        }
#if OS_EVENT_NAME_SIZE > 1
        pevent->OSEventName[0] = '?';                      /* Unknown name                             */
        pevent->OSEventName[1] = OS_ASCII_NUL;
#endif
        pevent->OSEventType    = OS_EVENT_TYPE_UNUSED;
        pevent->OSEventPtr     = OSEventFreeList;          /* Return Event Control Block to free list  */
        pevent->OSEventCnt     = 0;
        OSEventFreeList        = pevent;                   /* Get next free event control block        */
        OS_EXIT_CRITICAL();
        if (tasks_waiting == OS_TRUE)                      /* Reschedule only if task(s) were waiting  */
        {
            OS_Sched();                                    /* Find highest priority task ready to run  */
        }
        *err                   = OS_NO_ERR;
        pevent_return          = (OS_EVENT*)0;             /* Semaphore has been deleted               */
        break;

    default:
        OS_EXIT_CRITICAL();
        *err                   = OS_ERR_INVALID_OPT;
        pevent_return          = pevent;
        break;
    }
    return pevent_return;
}
#endif

/*$PAGE*/
/*
 *********************************************************************************************************
 *                                           PEND ON SEMAPHORE
 *
 * Description: This function waits for a semaphore.
 *
 * Arguments  : pevent        is a pointer to the event control block associated with the desired
 *                            semaphore.
 *
 *              timeout       is an optional timeout period (in clock ticks).  If non-zero, your task will
 *                            wait for the resource up to the amount of time specified by this argument.
 *                            If you specify 0, however, your task will wait forever at the specified
 *                            semaphore or, until the resource becomes available (or the event occurs).
 *
 *              err           is a pointer to where an error message will be deposited.  Possible error
 *                            messages are:
 *
 *                            OS_NO_ERR           The call was successful and your task owns the resource
 *                                                or, the event you are waiting for occurred.
 *                            OS_TIMEOUT          The semaphore was not received within the specified
 *                                                timeout.
 *                            OS_ERR_EVENT_TYPE   If you didn't pass a pointer to a semaphore.
 *                            OS_ERR_PEND_ISR     If you called this function from an ISR and the result
 *                                                would lead to a suspension.
 *                            OS_ERR_PEVENT_NULL  If 'pevent' is a NULL pointer.
 *
 * Returns    : none
 *********************************************************************************************************
 */

void  OSSemPend(OS_EVENT *pevent, INT16U timeout, INT8U *err)
{
#if OS_CRITICAL_METHOD == 3                           /* Allocate storage for CPU status register      */
    OS_CPU_SR cpu_sr = 0;
#endif



#if OS_ARG_CHK_EN > 0
    if (err == (INT8U*)0)                             /* Validate 'err'                                */
    {
        return;
    }
    if (pevent == (OS_EVENT*)0)                       /* Validate 'pevent'                             */
    {
        *err = OS_ERR_PEVENT_NULL;
        return;
    }
#endif
    if (pevent->OSEventType != OS_EVENT_TYPE_SEM)     /* Validate event block type                     */
    {
        *err = OS_ERR_EVENT_TYPE;
        return;
    }
    if (OSIntNesting > 0)                             /* See if called from ISR ...                    */
    {
        *err = OS_ERR_PEND_ISR;                       /* ... can't PEND from an ISR                    */
        return;
    }
    if (OSLockNesting > 0)                            /* See if called with scheduler locked ...       */
    {
        *err = OS_ERR_PEND_LOCKED;                    /* ... can't PEND when locked                    */
        return;
    }
    OS_ENTER_CRITICAL();
    if (pevent->OSEventCnt > 0)                       /* If sem. is positive, resource available ...   */
    {
        pevent->OSEventCnt--;                         /* ... decrement semaphore only if positive.     */
        OS_EXIT_CRITICAL();
        *err = OS_NO_ERR;
        return;
    }
    /* Otherwise, must wait until event occurs       */
    OSTCBCur->OSTCBStat   |= OS_STAT_SEM;             /* Resource not available, pend on semaphore     */
    OSTCBCur->OSTCBPendTO  = OS_FALSE;
    OSTCBCur->OSTCBDly     = timeout;                 /* Store pend timeout in TCB                     */
    OS_EventTaskWait(pevent);                         /* Suspend task until event or timeout occurs    */
    OS_EXIT_CRITICAL();
    OS_Sched();                                       /* Find next highest priority task ready         */
    OS_ENTER_CRITICAL();
    if (OSTCBCur->OSTCBPendTO == OS_TRUE)             /* See if we timedout                            */
    {
        OS_EventTO(pevent);
        OS_EXIT_CRITICAL();
        *err = OS_TIMEOUT;                            /* Indicate that didn't get event within TO      */
        return;
    }
    OSTCBCur->OSTCBEventPtr = (OS_EVENT*)0;
    OS_EXIT_CRITICAL();
    *err = OS_NO_ERR;
}
/*$PAGE*/
/*
 *********************************************************************************************************
 *                                         POST TO A SEMAPHORE
 *
 * Description: This function signals a semaphore
 *
 * Arguments  : pevent        is a pointer to the event control block associated with the desired
 *                            semaphore.
 *
 * Returns    : OS_NO_ERR           The call was successful and the semaphore was signaled.
 *              OS_SEM_OVF          If the semaphore count exceeded its limit.  In other words, you have
 *                                  signalled the semaphore more often than you waited on it with either
 *                                  OSSemAccept() or OSSemPend().
 *              OS_ERR_EVENT_TYPE   If you didn't pass a pointer to a semaphore
 *              OS_ERR_PEVENT_NULL  If 'pevent' is a NULL pointer.
 *********************************************************************************************************
 */

INT8U  OSSemPost(OS_EVENT *pevent)
{
#if OS_CRITICAL_METHOD == 3                                /* Allocate storage for CPU status register */
    OS_CPU_SR cpu_sr = 0;
#endif



#if OS_ARG_CHK_EN > 0
    if (pevent == (OS_EVENT*)0)                            /* Validate 'pevent'                        */
    {
        return OS_ERR_PEVENT_NULL;
    }
#endif
    if (pevent->OSEventType != OS_EVENT_TYPE_SEM)          /* Validate event block type                */
    {
        return OS_ERR_EVENT_TYPE;
    }
    OS_ENTER_CRITICAL();
    if (pevent->OSEventGrp != 0)                               /* See if any task waiting for semaphore*/
    {
        (void)OS_EventTaskRdy(pevent, (void*)0, OS_STAT_SEM);  /* Ready HPT waiting on event           */
        OS_EXIT_CRITICAL();
        OS_Sched();                                            /* Find HPT ready to run                */
        return OS_NO_ERR;
    }
    if (pevent->OSEventCnt < 65535u)                  /* Make sure semaphore will not overflow         */
    {
        pevent->OSEventCnt++;                         /* Increment semaphore count to register event   */
        OS_EXIT_CRITICAL();
        return OS_NO_ERR;
    }
    OS_EXIT_CRITICAL();                               /* Semaphore value has reached its maximum       */
    return OS_SEM_OVF;
}
/*$PAGE*/
/*
 *********************************************************************************************************
 *                                          QUERY A SEMAPHORE
 *
 * Description: This function obtains information about a semaphore
 *
 * Arguments  : pevent        is a pointer to the event control block associated with the desired
 *                            semaphore
 *
 *              p_sem_data    is a pointer to a structure that will contain information about the
 *                            semaphore.
 *
 * Returns    : OS_NO_ERR           The call was successful and the message was sent
 *              OS_ERR_EVENT_TYPE   If you are attempting to obtain data from a non semaphore.
 *              OS_ERR_PEVENT_NULL  If 'pevent'     is a NULL pointer.
 *              OS_ERR_PDATA_NULL   If 'p_sem_data' is a NULL pointer
 *********************************************************************************************************
 */

#if OS_SEM_QUERY_EN > 0
INT8U  OSSemQuery(OS_EVENT *pevent, OS_SEM_DATA *p_sem_data)
{
#if OS_LOWEST_PRIO <= 63
    INT8U     *psrc;
    INT8U     *pdest;
#else
    INT16U    *psrc;
    INT16U    *pdest;
#endif
    INT8U i;
#if OS_CRITICAL_METHOD == 3                                /* Allocate storage for CPU status register */
    OS_CPU_SR cpu_sr = 0;
#endif



#if OS_ARG_CHK_EN > 0
    if (pevent == (OS_EVENT*)0)                            /* Validate 'pevent'                        */
    {
        return OS_ERR_PEVENT_NULL;
    }
    if (p_sem_data == (OS_SEM_DATA*)0)                     /* Validate 'p_sem_data'                    */
    {
        return OS_ERR_PDATA_NULL;
    }
#endif
    if (pevent->OSEventType != OS_EVENT_TYPE_SEM)          /* Validate event block type                */
    {
        return OS_ERR_EVENT_TYPE;
    }
    OS_ENTER_CRITICAL();
    p_sem_data->OSEventGrp = pevent->OSEventGrp;           /* Copy message mailbox wait list           */
    psrc                   = &pevent->OSEventTbl[0];
    pdest                  = &p_sem_data->OSEventTbl[0];
    for (i = 0; i < OS_EVENT_TBL_SIZE; i++)
    {
        *pdest++ = *psrc++;
    }
    p_sem_data->OSCnt = pevent->OSEventCnt;                /* Get semaphore count                      */
    OS_EXIT_CRITICAL();
    return OS_NO_ERR;
}
#endif                                                     /* OS_SEM_QUERY_EN                          */

/*$PAGE*/
/*
 *********************************************************************************************************
 *                                              SET SEMAPHORE
 *
 * Description: This function sets the semaphore count to the value specified as an argument.  Typically,
 *              this value would be 0.
 *
 *              You would typically use this function when a semaphore is used as a signaling mechanism
 *              and, you want to reset the count value.
 *
 * Arguments  : pevent     is a pointer to the event control block
 *
 *              cnt        is the new value for the semaphore count.  You would pass 0 to reset the
 *                         semaphore count.
 *
 *              err        is a pointer to an error code returned by the function as follows:
 *
 *                            OS_NO_ERR            The call was successful and the semaphore value was set.
 *                            OS_ERR_EVENT_TYPE    If you didn't pass a pointer to a semaphore.
 *                            OS_ERR_PEVENT_NULL   If 'pevent' is a NULL pointer.
 *                            OS_ERR_TASK_WAITING  If tasks are waiting on the semaphore.
 *********************************************************************************************************
 */

#if OS_SEM_SET_EN > 0
void  OSSemSet(OS_EVENT *pevent, INT16U cnt, INT8U *err)
{
#if OS_CRITICAL_METHOD == 3                           /* Allocate storage for CPU status register      */
    OS_CPU_SR cpu_sr = 0;
#endif



#if OS_ARG_CHK_EN > 0
    if (err == (INT8U*)0)                             /* Validate 'err'                                */
    {
        return;
    }
    if (pevent == (OS_EVENT*)0)                       /* Validate 'pevent'                             */
    {
        *err = OS_ERR_PEVENT_NULL;
        return;
    }
#endif
    if (pevent->OSEventType != OS_EVENT_TYPE_SEM)     /* Validate event block type                     */
    {
        *err = OS_ERR_EVENT_TYPE;
        return;
    }
    OS_ENTER_CRITICAL();
    *err = OS_NO_ERR;
    if (pevent->OSEventCnt > 0)                       /* See if semaphore already has a count          */
    {
        pevent->OSEventCnt = cnt;                     /* Yes, set it to the new value specified.       */
    }
    else                                              /* No                                            */
    {
        if (pevent->OSEventGrp == 0)                  /*      See if task(s) waiting?                  */
        {
            pevent->OSEventCnt = cnt;                 /*      No, OK to set the value                  */
        }
        else
        {
            *err               = OS_ERR_TASK_WAITING;
        }
    }
    OS_EXIT_CRITICAL();
}
#endif

#endif                                                /* OS_SEM_EN                                     */
